None.
The present invention pertains to methods and apparatus for assisting a person when, alone or with others, he or she moves a ladder from place-to-place, as for example, from its storage place to a work site or one work site to another.
Many kinds of ladders and stepping-stools are known which are mounted on wheels and casters that automatically or manually retract when a person""s weight is placed on their steps. The casters facilitate movement of the ladder from one location to another. For safety purposes, the casters retract so that the ladder legs rest on the supporting surface, usually a floor or the ground. Some ladders are either too large or too cumbersome for one person to carry easily and without potential for injury. Some of these ladders use caddies, dollies or wheeled attachments to facilitate transport by a single person. However, many ladders are made with no such device.
U.S. Pat. No. 4,564,203 to Ronald Williams and dated Jan. 14, 1986, discloses an aid for transporting a narrow oblong object (such as a ladder leg 72. His device does not permit the ladder to be erected on the wheel-supported end without removing the concave socket and wheel assembly (releasable embodiment 70). Therefore this embodiment of the device is not easily usable on the step ladder shown earlier in the drawings since it can only be placed on the free end of the step ladder legs 33 and must be removed before that ladder can be erected in order that an appropriate surface support the ladder legs. That embodiment 70 is also not easily used on an extension ladder. Assuming that it is clamped to the topmost end of an erect ladder, an irregular and flimsy element 74, 79 is then placed against the wall against which the ladder top is supported, a potential safety hazard. If it is placed on the lower segment of the ladder, the socket interferes with the upper segment""s flush fit on the lower segment. In order to transport the it, the ladder must be fully lowered and then swung right or left or allowed to drag down the surface against which it was leaning in order to place the wheel on the ground or other supporting surface. This is difficult to do with very long or heavy ladders. The most appropriate position for this device being at the lower ends of the ladder legs, the user is compelled to remove it in order to safely mount the ladder. Williams has provided a narrow wheel for end support. His wheel, therefore, must be moved from side-to-side and pinned in place to prevent the ladder from tipping. Finally, since the ladder leg must fit into the concave socket 73, such a socket can not be sized universally for all sizes and shapes of ladder legs.
In his U.S. Pat. No. 3,580,601, dated May 25, 1971, Ray P. Miller discloses a skate device for transporting unwieldy, flat objects with ease. The device comprises an elongated base member containing a pair of brackets at each end and a clamping bracket member at its midsection. Rollers are provided on the bottom of the base member and are all in line. The end rollers are mounted slightly above the midsection roller to enable the skate to be tipped backward or forward on the end rollers for maneuverability. The skate is clamped to an edge of the flat object for transporting. Miller""s device is limited to placement along a thin edge of flat, heavy objects with large surface areas (col. 1, line 3-5) such as doors, sheet rock, plywood, etc. Its elongated base member is large, heavy, and can not reasonably be left in place on an ordinary ladder in use and therefore has marginal utility for ladder transport.
U.S. Pat. No. 5,566,780, dated Oct. 22, 1996 was issued to Harry M. Hambrough. It describes a combination cart and ladder apparatus including a first and a second ladder assembly. Such devices are often used for hunting. A pair of wheel assemblies are supported by the first ladder assembly at preselected positions on its length. Translation of the second ladder assembly with respect to the first ladder assembly is not interfered with by the wheel connection assemblies. A first platform assembly is connected to distal ends of second lateral support members. A stop element is connected to a bottom side of the first platform element. The stop element includes a fixed portion connected to the first platform element and a free-end portion projecting from the fixed portion at an obtuse angle. A strap assembly is connected to the first platform element and connects the apparatus to a tree. When the combination cart and ladder is used to provide an elevated platform in a tree, the fork assembly which holds the wheels is adjusted so they are no longer in contact with the ground. Wheel brakes are, therefore, not needed. Applicants"" wheels need no adjustment when the ladder is erected since they are placed in a position which obviates their contact with ground except when the ladder is being transported. Applicants"" ladder with transport attachment is not intended to be used as a cart for moving other objects.
Peter DiSario""s U.S. Pat. No. 5,727,799 presents a dolly for supporting a ladder during movement to a work site. The dolly has a frame adapted to be attached by clips to the rungs of the ladder. The dolly has a single, relatively large wheel in terms of ladder width pivotally mounted on the frame for supplying rolling support in order to enable a single individual to move a long, heavy ladder over sloping or rough ground. The wheel assembly is very large and because of its position in the center of the ladder side rails or legs where the user would ordinarily mount the ladder, it prohibits use of the ladder when it is erected, unless the wheel and frame are completely removed or the ladder can be placed against a wall allowing clearance for the wheel. With DiSario""s caddy, the ladder cannot be transported on its edge.
U.S. Pat. No. 5,086,872 to Fan-Nam Lim discloses a foldable ladder equipped with a pair of wheels so the ladder can be converted into a push cart for transportation of various goods with ease. The foldable ladder is made up of a number of sections joined together one by one by adjustable knuckles which can be put in a number of positions so the ladder can be transformed into a plurality of forms of cart when a pair of wheels are removably attached to the bottom of the ladder. The heavy-duty wheels and axle are not easily removed, being bolted to the ladder legs and spanning across the width of the ladder. This configuration permits transport of the ladder device basically as a cart, the width being constrained parallel to the supporting surface, floor or ground. As a result, the ladder can not be transported on edge as may be required to pass through narrow doorways.
Brookes et al. in their U.S. Pat. No. 4,049,283 describe a caddy for transporting a heavy ladder to a work site. The caddy is formed of a pair of transverse pieces having resilient clips installed thereon adapted to engage and clamp onto any rung of the ladder. The pieces are attached at spaced positions to the bridge of a two-wheeled carriage so that the pieces are adapted to straddle and engage a pair of adjacent rungs on the ladder in wheel-barrow position. The caddy must be disengaged and removed from the ladder before the ladder can be erected for use.
James R. Wilson in his U.S. Pat. No. 5,382,032, dated Jan. 17, 1995 discloses a wheeled stepladder dolly wherein the dolly is engageable with both a step of the ladder and existing cross braces on the support portion of a conventional stepladder to temporarily hold the step ladder in fixed relationship with the dolly, thus providing a stepladder dolly assembly to be used for transporting heavy boxes of tools and the like. The engagement means are adjustable and configured to be adaptable for a number of brands and varieties of commercially available stepladders. Wilson describes a means for transporting a stepladder and heavy objects placed on the face of the ladder. However, it appears that the step ladder must be disengaged from the dolly before it can be used as a ladder. In addition this device does not appear suited for long ladders unless they can be folded or collapsed somehow. The ladder can not be transported on edge with this device.
U.S. Pat. No. 5,105,908 was issued to Harvey J. Freund on Apr. 21, 1992. It reveals a kit which may be used to convert a ladder tree stand into a towable trailer that may be connected to a motorized vehicle. The trailer kit comprises a transport frame, tow frame attachment members, associated bolts and clamping plates. This conversion takes considerable time to assemble, is very large and heavy and is clearly not suitable for transporting a ladder from work site to work site by a single individual using only his or her own effort.
U.S. Pat. No. 5,232,233 by John Jedora describes a portable wheel assembly provided with a parallel type clamping system for attachment to objects, such as the transom of a car-top boat. An improved clamping effect is obtained by using xe2x80x9cUxe2x80x9d shaped tubing that embraces the wheel. While such a device might be adaptable in some way to transport a heavy ladder, Jedora does not indicate how this might be done. The wheel assemblies are complicated, very large, heavy, and relatively expensive for the purposes desired by Applicants.
U.S. Pat. No. 5,882,023 issued to William F. Swager discloses a wheeled transport device for maneuvering elongated objects in a simplified manner. It is remarkably similar in form and function to DiSario""s Patent described above. FIG. 1 shows a relatively large wheel on an axle disposed on a frame which is connected by brackets to the steps of a ladder. As in DiSario""s device, the wheel assembly is very large and because of its position in the center of the ladder side rails or legs where the user would ordinarily mount the ladder, it prohibits use of the ladder when it is erected, unless the wheel and frame are completely removed or the ladder can be erected with the wheel facing a wall. Additionally, as with DiSario""s caddy, the ladder cannot be transported on its edge.
In U.S. Pat. No. 3,841,437 by John W. Caughey, issued Oct. 15, 1974, a stool suitable for standing upon to reach high places is described. The stool includes an upstanding post to be grasped by the user and includes a roller which is normally inactive but which, when the stool is tilted, becomes active enabling the stool to be rolled about easily.
U.S. Pat. No. 4,063,616 to Ernest F. Gutierrez, issued Dec. 20, 1977 discloses a safety ladder assembly having a plurality of steps and at least three support feet for supporting the ladder on a horizontal surface. The assembly includes a caster assembly having at least three casters providing for rollingly transporting the ladder from one location to another. The casters are conjointly movable between a retracted storage position in which the support feet stably support the ladder on a horizontal surface and a second transporting position in which they stably support the ladder on the horizontal surface with the support feet elevated so the ladder may be rollingly transported along the surface. A linkage interconnects the casters so that they may be raised and lowered via actuating and retracting pedals.
U.S. Pat. No. 5,082,086 was issued to James F. Kerr on Jan. 21, 1992. The patent discloses a ladder including wheels normally received off the ground, and four legs normally supporting the ladder. When it is desired to move the ladder, it is pivoted off the legs until the wheels contact the ground and fully support the ladder. The ladder may then be moved. A rail includes an angled portion which provides a handle allowing the ladder to be easily moved. The wheels are preferably mounted above the ground by a distance between its radius and its diameter such that when the ladder is supported on the wheels, the legs will not interfere with the ground.
The above described apparatus"" would seem to add unneeded complication to a rather simple device, the ladder. The movable and retractable casters described add weight, size and cost to the ladder assemblies. They also require that the assembly have a large footprint which increases the storage space needed. They also seem impracticable for fixed or non-collapsible ladders used to climb to a great height. In addition, the casters and wheels of such assemblies are not easily transferrable to another ladder, adding to the total cost of ladder inventories needed by maintenance organizations. Because of the need to have the ladder""s legs rest securely on a supporting surface, a great deal of attention must be paid to the security of any retraction mechanism. Problems arise with prior art ladders having spring-loaded wheels which are biased into the supporting surface and require a user""s weight on the ladder to force the legs into contact with the ground for firm support. A user sometimes has the impression that the ladder is not sturdy, an undesirable condition.
Therefore, it is an object of the present invention to provide methods and apparatus to easily transport a ladder which does not have the undesirable characteristics of the schemes described above.
Another advantage of the present invention is to allow the ladder to be transported on edge since it may be required to pass through narrow doorways. Placement of a wheel attachment in respect of the ladder leg should permit the use of a pivot pin for castering, enhancing the maneuverability of the object when being transported on edge or otherwise.
It is also an object of the present invention to provide a wheeled attachment that need not be disengaged and removed from the ladder before the ladder can be erected for use. If the invention does not interfere with the ladders erection or support, it may always be left in place. Moreover, the ladder should be easily lowered to the transport position by one person by xe2x80x9cwalkingxe2x80x9d the ladder backward until the lower end rests on the transport wheel or wheels, and vice versa. Wheels should be wide, eliminating the necessity of adjusting them accurately under the plane of weight symmetry.
Yet another advantage of the present invention is to attach almost universally to any type and size of ladder so it can easily be moved from one ladder and placed on another. While a manufacturer can install the invention on new products, a user can use the invention on already-acquired ladders.
The development of a simple ladder transportation system which would reduce or obviate the need for retraction, weight, size and cost, yet still allow one person to easily maneuver and transport a ladder from place-to-place without injury, would constitute a major advance and would satisfy a long felt need in the construction and maintenance industries.
The present invention, Ladder Transport System, provides methods and apparatus to aid a user in transporting the ladder from place to place. Means for affixing a supporting wheel near the end and the edge of a ladder leg are described. The wheel may be allowed to pivot or xe2x80x9ccasterxe2x80x9d for enhanced maneuverability. In a preferred embodiment, the wheel assembly comprises dual caster wheels, of approximately two-inches diameter or larger. The axes of rotation of the wheels are disposed orthogonally so that at the users option the ladder can be transported on edge or with its face horizontal. The wheel size may be adjusted to the size and type of the ladder to be transported. The Ladder Transport System, called Ladder Dolly(trademark) by the inventors, can be affixed to nearly any existing ladder, permanently or removably. If desired, two dual-caster wheel assemblies can be used, each one being installed on a principal leg of the ladder. The removable wheel assembly is attached preferably with a single clamp screw, but may be permanently affixed to the ladder, for example, with welds, rivets or bolts.
A permanent or removable wheel of the present invention can be applied to nearly any type of ladder at the point of manufacture. A ladder manufacturer can adapt the invention to his specific type of equipment. The ladder may be one piece, or a multi-segment extension ladder. It may range from a simple step-ladder to a multi-story firemen""s ladder. It may be of wood, metal or other suitable material.
The caster wheel revolves on an axle which is supported at each end by a wheel bracket. The closed side of the wheel bracket, which parallels the axle, is joined to the back side of a xe2x80x9cCxe2x80x9d clampxe2x80x94that is the side of the xe2x80x9cCxe2x80x9d clamp which is opposite the ladder surfaces against which the clamp frame rests. The wheel bracket may be solidly fixed to the clamp frame or allowed to swivel on a pin about a pivot axis. The clamp frame is placed against the outside surface of a leg of the ladder and the threaded screw of the clamp is tightened down against the flat, inside surface of the ladder""s leg. The clamp frame is oriented so that when assembled to one end of a ladder""s leg and the ladder is placed with the side of that leg facing a supporting surface, usually the ground or floor, a wheel lies tangent to the supporting surface. The wheel will roll on that supporting surface when a person picks up the free end of the ladder and carries it along.
In a dual-caster wheel assembly, a second caster wheel, approximately identical to the first caster wheel, is disposed on the clamp frame orthogonal to the first caster wheel. The second caster wheel revolves on an axle which is supported at each end by a second wheel bracket. The closed side of the second bracket which parallels the second axle is joined to the side of the clamp frame.
If two dual-caster wheel assemblies are attached to a ladder, one on each principal leg, the ladder may be rotated with its face parallel to the ground or floor, so the ladder end rests on two wheels. This configuration will stably support very large ladders. The ladder can then be propelled by a person carrying the free end in the manner of a wheelbarrow.
When the wheel assembly or assemblies are so attached at one end of the ladder, and the opposite end is supported by a person, the wheel assembly or assemblies can be made to carry a large portion of the weight of the ladder. This relieves the person who must carry a ladder from place-to-place of considerable stress to his or her arms, shoulders, back, wrists, ankles, knees, etc. The portion of weight supported by the person is, of course, the ratio of distance from the center of the wheel to the center of gravity of the ladder to distance from the center of the wheel to where the person grasps the ladder. Thus, repeated use is much less stressful than carrying the entire weight of the ladder. For persons who use ladders frequently in their occupations such as firemen, electricians, carpenters, handymen and tradesmen, the Ladder Dolly(trademark) can help prevent personal injuries caused by the repeated use and transport of ladders. In addition, with the wheel assembly or assemblies so affixed, even very large ladders are easily maneuvered over most types of terrain.
A carrying handle, in one preferred embodiment fabricated of Velcro(trademark) material, may be attached to the ladder leg""s at the free end of the ladder. The handle allows the user to carry and pull the ladder while leaving one hand free to open doors or perform other operations.
An alternate embodiment of the Ladder Dolly(trademark) features two single-caster wheel assemblies, each one being installed on a principal leg of a ladder with the rotational axes of the wheels lying in a plane parallel to the face or width of the ladder.
The invention is a useful tool in virtually any industry, office or home where ladders are used, but especially in the construction and maintenance industries. Because of the placement of the wheel assembly, it is possible for one person to maneuver a ladder through and around narrow passageways such as doorways and around corners. The ladder with attached wheels can be erected and operated without inhibiting or interfering with the normal opening, closing, extending or retracting functions.
The present invention is also useful for elderly persons, particularly homeowners who have only occasional need to use a ladder. The Ladder Dolly(trademark) will undoubtedly become an indispensable part of manufactured ladders and will be sold to present ladder owners.
An appreciation of the other aims and objectives of the present invention and a more complete and comprehensive understanding of this invention may be obtained by studying the following description of a preferred embodiment, and by referring to the accompanying drawings.